Question:

What do C and D represent on the curve?

Answer:

C and D represent two points on the curve. The exact values of C and D will depend on the specific curve in question. To determine the exact values of C and D, the equation of the curve must be known. Once the equation of the curve is known, C and D can be determined by solving the equation for the two points.

Question:

Suppose there were plants that had a high concentration of Chlorophyll b, but lacked chlorophyll a, would it carry out photosynthesis? Then why do plants have chlorophyll b and other accessory pigments?

Answer:

1. No, plants that lack chlorophyll a would not be able to carry out photosynthesis because chlorophyll a is the primary pigment responsible for absorbing light energy and initiating the process of photosynthesis.

2. Plants have chlorophyll b and other accessory pigments to help them absorb additional wavelengths of light and increase the efficiency of photosynthesis. Chlorophyll b and other accessory pigments are able to absorb light energy that chlorophyll a cannot, allowing plants to use more of the available light energy for photosynthesis.

Question:

RuBisCo is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RuBisCO carries out more carboxylation in C4​ plants ?

Answer:

Step 1: Understand the question. The question is asking why RuBisCO carries out more carboxylation in C4 plants.

Step 2: Research RuBisCO and C4 plants. Research suggests that RuBisCO is an enzyme found in plants that acts both as a carboxylase and oxygenase. C4 plants are plants that use a specialized form of photosynthesis called C4 photosynthesis. This type of photosynthesis is more efficient than other forms of photosynthesis, and it helps the plant to conserve water and to cope with high temperatures.

Step 3: Analyze the relationship between RuBisCO and C4 plants. The relationship between RuBisCO and C4 plants is that C4 plants have a higher rate of carboxylation due to their more efficient photosynthesis process. This means that RuBisCO carries out more carboxylation in C4 plants because it is able to take advantage of the increased efficiency of C4 photosynthesis.

Question:

Give comparison between the following: (a) C3​ and C4​ pathways (b) Cyclic and non-cyclic photophosphorylation (c) Anatomy of leaf in C3​ and C4​ plants.

Answer:

(a) C3 and C4 Pathways: • C3 pathways involve the conversion of carbon dioxide into a 3-carbon molecule using the enzyme RuBisCO. • C4 pathways involve the conversion of carbon dioxide into a 4-carbon molecule using the enzyme PEP carboxylase. • C3 pathways are more common in plants and are found in most plants, while C4 pathways are found in only a few plants.

(b) Cyclic and Non-cyclic Photophosphorylation: • Cyclic photophosphorylation involves the production of ATP using light energy, with the electrons being recycled back to the reaction center. • Non-cyclic photophosphorylation involves the production of ATP using light energy, with the electrons being used to reduce NADP+ to NADPH. • Cyclic photophosphorylation is more efficient than non-cyclic photophosphorylation, as it does not require the use of NADP+.

(c) Anatomy of Leaf in C3 and C4 Plants: • C3 plants have leaves with a single layer of mesophyll cells, while C4 plants have leaves with two layers of mesophyll cells. • C3 plants have a single type of chloroplast, while C4 plants have two types of chloroplasts: bundle sheath and mesophyll cells. • C3 plants have a single type of enzyme for carbon dioxide fixation, RuBisCO, while C4 plants have two types of enzymes for carbon dioxide fixation, PEP carboxylase and RuBisCO.

Question:

By looking at a plant externally can you tell whether a plant is C3​ or C4​. Why and how ?

Answer:

Answer: No, you cannot tell whether a plant is C3 or C4 just by looking at it externally. This is because both C3 and C4 plants look the same on the outside. To determine which type of plant it is, you would need to analyze its photosynthetic pathway. This can be done by measuring the ratio of carbon dioxide to oxygen in the leaves of the plant during photosynthesis. C3 plants have a ratio of 1:1, while C4 plants have a ratio of 4:1.

Question:

By looking at which internal structure of a plant can you tell whether a plant is C3​ or C4​? Explain.

Answer:

1. The internal structure of a plant that can be used to tell whether it is C3 or C4 is the type of photosynthesis pathway it uses.

2. C3 plants use the Calvin cycle for photosynthesis, while C4 plants use the Hatch-Slack pathway.

3. C3 plants utilize only one enzyme in the Calvin cycle, RuBisCO, while C4 plants use two enzymes, PEP carboxylase and RuBisCO.

4. The RuBisCO enzyme in C3 plants is located in the mesophyll cells, while in C4 plants it is located in the bundle sheath cells.

5. C3 plants also have a higher rate of photorespiration than C4 plants.

Question:

Even though a very few cells in a C4​ plant carry out biosynthetic Calvin pathway, yet they are highly productive. Can you discuss why ?

Answer:

1. C4 plants are a type of plants that have evolved an efficient photosynthetic pathway to maximize their productivity in hot and dry climates.

2. This pathway involves the use of a special enzyme called PEP carboxylase, which helps the plant to capture and fix carbon dioxide more efficiently than C3 plants.

3. The C4 pathway also involves a process called “C4 acid cycle”, where the plant stores the fixed carbon dioxide in the form of four-carbon molecules, which are then used for the production of sugars.

4. This process is more efficient than the C3 pathway as it allows the plant to use less energy and water to produce sugars.

5. Furthermore, the C4 plants are able to use the energy of the sun more efficiently, as they can capture and store more carbon dioxide when compared to C3 plants.

6. This leads to higher productivity in C4 plants, even though only a few cells carry out the biosynthetic Calvin cycle.

Question:

Give comparison between the following : (a) C3​ and C4​ pathways, (b) Cyclic and noncyclic photophosphorylation. (c) Anatomy of leaf in C3​ and C4​ plants.

Answer:

(a) C3 and C4 Pathways:

C3 Pathway: The C3 pathway is the most common type of photosynthesis in which the first stable product of carbon fixation is a 3-carbon compound. It is also known as the Calvin cycle.

C4 Pathway: The C4 pathway is an adaptation of the C3 pathway that is found in some plants, especially those in hot, dry climates. It involves the use of an additional enzyme and an additional carbon fixation step to produce a 4-carbon compound as the first stable product of carbon fixation.

(b) Cyclic and Noncyclic Photophosphorylation:

Cyclic Photophosphorylation: Cyclic photophosphorylation is a process in which electrons are passed from photosystem II to photosystem I and back to photosystem II in a cyclic manner. This process produces ATP but no NADPH.

Noncyclic Photophosphorylation: Noncyclic photophosphorylation is a process in which electrons are passed from photosystem II to photosystem I and then to an electron acceptor. This process produces both ATP and NADPH.

(c) Anatomy of Leaf in C3 and C4 Plants:

C3 Plants: In C3 plants, the leaves are typically thin and flat, with a large surface area to absorb light. The veins are typically branched and arranged in a net-like pattern. The stomata are located on the upper and lower surfaces of the leaf and are used to regulate gas exchange.

C4 Plants: In C4 plants, the leaves are typically thick and waxy, with a smaller surface area to absorb light. The veins are typically parallel and arranged in a linear pattern. The stomata are typically located on the lower surface of the leaf and are used to regulate gas exchange.

Question:

Why the colour of a leaf kept in the dark frequently is yellow or pale green? Which pigment do you think is more stable?

Answer:

1. Leaves contain two types of pigments: chlorophyll and carotenoids. Chlorophyll is responsible for the green colour of leaves, while carotenoids are responsible for the yellow and pale green colours.

2. When a leaf is kept in the dark, the chlorophyll breaks down faster than carotenoids, resulting in the leaf taking on a yellow or pale green colour.

3. Carotenoids are more stable than chlorophyll, so they are more likely to remain intact even when the leaf is kept in the dark.

Question:

Look at leaves of the same plant on the shady side and compare it with the leaves on the sunny side or compare the potted plants kept in the sunlight with those in the shade. Which of them has leaves that are darker green? Why?

Answer:

Step 1: Examine the leaves of the same plant on the shady side.

Step 2: Compare the leaves on the shady side to the leaves on the sunny side.

Step 3: Observe which of the leaves are darker green.

Step 4: Determine why the leaves on the shady side are darker green. This is likely due to the fact that the shady side does not receive as much direct sunlight, which limits the amount of photosynthesis that takes place in the leaves.